This invention relates to an eraser, ability of which for erasing characters and the like on a paper written with ball-point pen, fountain pen, typewriter, word processor, color pencils or the like is improved, and to a method for manufacturing such improved eraser.
A so-called sand-containing eraser has been heretofore known as an eraser for erasing characters and the like written on a paper with ball-point pen, fountain pen or the like. A conventional sand-containing eraser is manufactured in such a manner that a factice (white factice), a plasticizer, and a mineral oil are mixed homogeneously with rubber or plastic, a major component, to which is added an abrasive material having a particle size of about 150 emery, carborundum (black silicon carbide) or the like, the resulting admixture is kneaded by the use of rolls or the like, and the product thus kneaded is either vulcanized or heated and shaped.
The structure of the shaped eraser is shown in FIG. 2 wherein particles of an abrasive material 12 are dispersed and included in a homogeneous major eraser material 10.
In said conventional sand-containing eraser, if the major eraser material 10 is a soft material, such major eraser material does not present suitable stiffness to sustain particles of the abrasive material 12 as shown in FIG. 3 in the case when the eraser itself is pressed against the surface of a paper 14. Thus, such eraser cannot scrape the ink 16 bonded to the paper surface 14 therefrom so that such conventional eraser has poor erasing ability.
On the other hand, if the major eraser material 10 is a hard material, such hard major eraser material 10 cannot be in close contact with the paper surface 14 as shown in FIG. 4. Accordingly, if there is a minute irregularity on the paper surface 14, particles of the abrasive material 12 included in such hard eraser cannot fit into the minute irregularity so that the abrasive material particles 12 cannot scrape off the ink 16 on the paper surface 14. In this case, it is required to scrape off the paper 14 itself up to such a depth corresponding to that where the ink 16 exists, so that there is such a disadvantage that the paper 14 is damaged by such hard eraser in the case where a soft paper is used, whilst if a hard paper is employed, the paper 14 cannot be scraped off by the eraser so that the ink 16 on the paper surface remains unerased.
In view of the above, the present invention contemplates to eliminate disadvantages involved in the above described prior art and to provide an improved eraser through the use of which damage of a paper to be erased decreases, besides erasing ability of the eraser is elevated, as well as a method for manufacturing such improved eraser.